Every villainous team needs a genius, a leader, and someone who just oozes death. Sidious is all of these things. Anyone who can lead a monstrously oppressive empire successfully(ish) is obviously a tactical genius. He is really old as well, making him an obvious leader. He also literally has a dark aura about him, Ya know, the force. Don't think however he wouldn't be able to keep up with a young, spry team either. I mean come on, he shoots lighting out of his hands. He easily fills a genius leader role on a villain team.
Villains love style. Just ask.... Any villain really. Beyond the sick wheels seen in Captain America: The First Avenger, he is also the result of a failed experiment, and is pretty solid with a gun. This sounds like an amazing villain team member by any standards, but his presence could certainly add depth of plot to a movie, with his strong leadership skills on display he may struggle with Sidious for leadership of a kick-ass team. It's only natural to want to have this kind of power at your fingertips.
As proven in the latest avengers movie, every good team of fighters needs someone who can hit a bullseye, snipe an enemy, or cover a charge. Deadshot certainly fits this type. He also is an actual member of the suicide squad, adding to some consistancy. And I can't get over how his targeting system on his face looks like a monacle. Talk about smooth.
Every team needs somebody to take orders and jack stuff up. He is also a zombie. If that doesn't say bad, I don't know what will.
So there you have it. A better suicide squad. There is a definite air of badness. I also tried to stick to comics, because that is where all the best villains come from. I bet they could get 3-400 kills in one feature film alone.